`merge_arrs` might overwrite fields unintended

[dachengx]

strax/strax/utils.py

Lines 204 to 207 in 8389ea6

	result = np.zeros(n, dtype=dtype)
	for arr in arrs:
	for fn in arr.dtype.names:
	result[fn] = arr[fn]

If you have two chunks, say a and b then you want to merge them, the result depends on the order of these two variables.

import numpy as np
import strax


n = 3
a = np.empty(n, dtype=strax.time_fields)
a['time'] = range(n)
b = np.empty(n, dtype=strax.time_fields)
b['time'] = a['time'][::-1]

print(a['time'])
print(b['time'])
print(strax.merge_arrs([a, b])['time'])

output:

[0 1 2]
[2 1 0]
[2 1 0]

at least a warning should be shown in such cases.